Openqa-client

1. **API**: remove `WaitError` exception
2. Update release script to use Python 3, publish to PyPI
3. Update setup.py for current best practices
4. Don't modify original request in `_add_auth_headers`
5. Don't edit list while iterating it in `find_clones`
6. Add a test suite, tox config and GitHub Actions-based CI

1. Fix long description for PyPI

1. Update constants to reflect upstream changes again, including
some additions and **REMOVAL** of JOB_INCOMPLETE_RESULTS

1. Update constants to reflect upstream changes (again)

1. Update constants to reflect upstream changes

1. First proper release